JP3340165B2 - Moving body traveling direction identification circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile object receiving information from a radio transmitter installed on a road, and improving the reliability of identifying the traveling direction of the mobile object from the obtained information. And a traveling direction identification circuit.

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
Road-to-vehicle communication is performed between a wireless transmitter (beacon) installed on the road at a predetermined distance and an in-vehicle device, and using this communication means, the position of a passing point, the shape of an intersection, destination guidance, or change is performed. Some traffic information is transmitted to a navigation system or the like.

FIG. 6 is a diagram schematically showing a roadside-to-vehicle communication system of a mobile body. As shown in this figure, a wireless transmitter on the road provides information to the vehicle, relative to a receiver of the vehicle facing the road. When the information provided by the wireless transmitter to the vehicle depends on the traveling direction of the vehicle (for example, destination guidance),
The radio transmitter must include the direction information in the information so that vehicles in the opposite direction do not process the information. For that purpose, it is necessary for the receiver to identify the traveling direction of the own vehicle with respect to the beacon. The system shown in FIGS. 6 and 7 is used as the system for identifying the traveling direction. That is, the radio wave frequency-modulated (FSK) or phase-modulated by the road information data is divided into two waves, and AM waves having different phases are applied to radio waves radiated in the front-rear direction of the road (the left-right direction of the road viewed from the beacon). AM1 and AM2) are superimposed,
Transmit from beacon. In a vehicle, the AM reception signal is
When the signal changes from one signal to the AM2 signal, the traveling direction is identified as the forward direction, and when the signal changes from the AM2 signal to the AM1 signal, the traveling direction is identified as the reverse direction. Hereinafter, this identification will be described in detail.

FIG. 8 is a diagram showing a conventional circuit for identifying the traveling direction, and FIG. 9 is a diagram showing a timing chart of the operation of the traveling direction identification circuit of FIG. The traveling direction identification circuit shown in FIG. 8 includes a shift register 200 that sequentially stores the AM1 and AM2 signals reproduced by the receiver of the vehicle using a reproduction clock ck2 described later, and a logical sum of the data stored in the shift register 200. A first AND circuit 201 which takes a logical value, and a second AND circuit 202 which takes the inverted logic of the data.
including.

A data modulated wave signal from the radio transmitter shown in FIG. 9A and a reproduced AM1 signal shown in FIG. 9D (solid line)
As described above, the reproduced AM2 signal (dotted line) is synchronized with the reproduced AM2 signal, and a reproduced clock 1 synchronized with the data modulated wave signal is generated.
A reproduction clock 2 shifted by an angle of ° is generated. The receiver receives only the AM1 signal (represented by a solid line in the drawing) before the vehicle passes through the transmitter in the forward direction of the vehicle, and thus the reproduced AM1 signal is taken into the shift register 200 every time the reproduction clock 2 rises. All the bits become "1" and hold this state, and at the same time, the output of the first AND circuit 201 holds "1". On the other hand, the output of the second AND circuit 202 holds “0”. In this case, it is determined that the AM1 signal is being received.

Since the receiver receives only the AM2 signal (represented by a dotted line in the figure) after the vehicle travels in the forward direction and passes through the transmitter, the reproduction A starts every time the reproduction clock 2 rises.
The M2 signal is taken into the shift register 200, and all the bits become "0" and are held. It is inverted at the input of the second AND circuit 202 and its output becomes "1". On the other hand, the output of the first AND circuit 201 is held at “0”. In this case, it is determined that the AM2 signal is being received. That is, when the outputs of the first AND circuits 201 and 202 are “1” and “0”, the AM1 signal is being received,
Further, in the case of “0” and “1”, it is determined that the AM2 signal is being received.

In this case, when the outputs of the first and second AND circuits 201 and 202 change from "1" and "0" to "0" and "1" due to passing right below the transmitter, the traveling direction of the vehicle is changed. It is identified as forward. When the traveling direction of the vehicle is the reverse direction, the operation is the reverse of the above and the description is omitted. However, the outputs of the first two AND circuits 201 and 202 are changed from “0” and “1” to “1” and When it changes to "0", it is identified that the traveling direction of the vehicle is the reverse direction.

By the way, even if the received electric field weakens instantaneously and the vehicle travels in the forward direction and receives the AM signal before passing through the transmitter, some bits of the shift register 200 contain “0”; Therefore, the output of the first AND circuit 201 changes from “1” to “0”. In this case, the output of the second logic circuit 202 holds “0”. After passing through the transmitter, the output of the first AND circuit 201 is “0”.
Even if the M2 signal is received, if "0" is included in some bits of the shift register 200 due to a weak reception electric field, the output of the second AND circuit 202 should be "1" but "1" To “0”. Therefore, the first and second AND circuits 20 can pass even immediately under a beacon having a transmitter.
The outputs of 1 and 202 are both “0”. In this case, it is determined that the traveling direction cannot be identified due to an instantaneous weak reception electric field, and the traveling direction is not determined, thereby avoiding erroneous identification.

As described above, the current process is continued when the traveling direction is identified at the place where the signal is to be received, but if the traveling direction cannot be identified, another backup process is performed.

[0010]

However, in the conventional traveling direction discriminating circuit, the following problems occur when the received electric field is not instantaneous but weak for a long period of time. FIG. 10 is a diagram showing a decrease in the level of the AM reproduction signal when the reception electric field is weak. As shown in the figure, the AM1 and AM2 signals become low, for example, when the traveling direction is the forward direction and the AM
When the level of the 1 signal is low, all bits of the shift register 200 take in “0”, the output of the first AND circuit 201 is “0”, but the output of the second AND circuit 202 is “1”. And the same state is maintained after passing through the transmitter. The same is true even if the running direction is reverse. That is, the output of the first AND circuit is always "0" and the output of the second AND circuit 202 is always "1". In this case as well, the traveling direction cannot be identified. For this reason, it is determined that the traveling direction cannot be identified, and another backup process is performed.

However, such a state occurs when all the bits of the shift register 200 are stuck to "0" due to a failure in the receiver for extracting the AM signal, or when the second AND circuit 202 is stuck high. May occur. Since this phenomenon is similar to the long-term weak reception electric field described above,
There is a problem that the two cannot be distinguished, and even if there is a failure, the process proceeds to another backup signal processing.

In a weak reception electric field, noise is mixed. If this noise has the same frequency as the AM signal, A
There has been a problem that reception (demodulation) of the M signal becomes unstable and erroneous identification is performed in the traveling direction. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a traveling direction discriminating circuit for a moving object capable of stably discriminating the traveling direction even with a weak reception electric field.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention solves the above-mentioned problems by providing data from a radio transmitter installed on a road, a traveling direction synchronized with the data, and a square having mutually opposite phases. A clock generation unit, a first shift register, a second shift register, a first AND unit, and a second AND unit are provided in a traveling direction identification circuit of a moving object that receives a wave.

The clock generating means reproduces a reproduction clock ck2 having the same period as the square wave indicating the running direction and a phase shift of 90 ° and a reproduction clock ck3 having an opposite phase to the reproduction clock ck2. A clock is generated. The first shift register fetches and shifts a square wave indicating the running direction as bit data for each of the reproduction clocks ck2.

The second shift register fetches and shifts a square wave indicating the running direction as bit data for each reproduction clock ck3. The first
Is obtained by taking the logical product of each bit data fetched by the first shift register and each bit data fetched by the second shift register and inverted.

The second AND means calculates the AND of each bit data taken in and inverted by the first shift register and each bit data taken by the second shift register. And a stabilizing circuit for detecting the duty ratio of the square wave and passing the outputs of the first and second AND means and the output only when the duty ratio is constant.

[0017]

According to the circuit for discriminating the traveling direction of a moving body of the present invention,
A reproduced clock ck2 and a reproduced clock c having the same cycle as the square wave indicating the running direction and shifted by 90 ° in phase.
A reproduction clock ck3 having a phase opposite to that of k2 is formed. The first shift register fetches a square wave indicating the running direction as bit data for each reproduction clock ck2, and shifts one level of the square wave. In the second shift register, a square wave indicating the running direction is fetched and shifted as bit data for each reproduction clock ck3, and only the other level of the square wave is continuously held for a certain period of time. . The logical product of each bit data taken in the first shift register and each bit data taken in the second shift register and inverted is taken, and further, each bit data taken in the first shift register and inverted is taken. By taking the logical product of the bit data and each bit data taken into the two shift registers, if the square wave is normal for a certain period of time, the result of one logical product is "1" and the other logical product is "1". The result of the product is "0". When the backward waveform immediately below the beacon, which is the transmitter, is inverted, the result of the logical product of the two is inverted, and the inversion identifies the traveling direction. However, when a weak reception electric field is instantaneously generated, the logical product "1" changes to "0". In this case, there is no inversion as described above in the result of the two logical products immediately below the beacon, and in this case, the identification of the traveling direction is not performed, thereby preventing the erroneous identification of the traveling direction.
When a square wave is not formed due to a weak reception electric field for a certain period of time, one logical product is “1” and the other logical product is “0”. The logical product of the two is not changed and distinguished from the phenomenon of the failure of the traveling direction identification circuit. In this case, the traveling direction is not identified, and the identification of the traveling direction is prevented. In addition, even if the signal is affected by noise due to the weak reception electric field and the two logical products "1" and "0" are inverted in the traveling direction discriminating circuit, the duty ratio of the square wave is monitored, and the duty ratio is kept within a certain range. If it deviates, it is determined that the received electric field is weak and noise is mixed in, so that the identification of the traveling direction is not performed and the instability of the identification can be prevented.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of a traveling direction identification circuit for a moving object according to an embodiment of the present invention. The traveling direction discriminating circuit 150 of the moving object shown in the figure includes a receiver 2 for receiving data transmitted from a wireless transmitter on the road via the antenna 1.
A clock generating means 3 for detecting a start position of data from the CPU and supplying a clock signal to fetch and shift data into a shift register described later in synchronization with the start position, and a clock signal generated by an AM signal of the receiver 2. Means 3
Means 4 for synchronizing the clock signal with the clock signal and forming a reproduction clock ck1;
A 90 ° phase shifter 5 for shifting the phase of the clock signal 1 by 90 °, and a reproduction clock c connected to the 90 ° phase shifter for inverting its output signal.
Inverter 6, which forms the k3 signal, and data from the receiver 2 which is fetched by the recovered clock ck2 from the 90 ° transferer 5 and at the rising edge of the recovered clock ck3 from the inverter 6, respectively, and shifts the fetched data. And 2
Shift registers 7 and 8 and the first shift register 7
First AND means 9 for calculating the logical product of each output of the second shift register 8 and each inverted output of the second shift register 8, and the logic of each inverted output of the first shift register 7 and each output of the second shift register 8 Second AND means 10 for taking a product.

Here, the data transmitted by the receiver 2 from the beacon wireless transmitter include a data modulation wave signal irrespective of the traveling direction, a frequency modulation (FSK) of a digital signal,
Data AM1 and A, which are transmitted by phase modulation (PSK) and indicate the running direction, are AM-modulated (ASK) by square waves having a phase opposite to each other in the forward and reverse directions of the vehicle.
Some M2 signals are transmitted. The AM1 and AM2 signals are superimposed on the data modulated wave signal.

FIG. 2 is a diagram showing a timing chart in the traveling direction identification circuit of FIG. As shown in this figure,
The reproduction clock ck1 is formed in synchronization with the start position of the received data by the synchronization means 4, the reproduction clock ck2 is formed by shifting the reproduction clock ck1 by 90 degrees by the 90 ° phase shifter 5, and the reproduction clock ck2 is generated by the inverter 6. Is inverted to form a reproduction clock ck3. Before the vehicle equipped with the receiver passes the transmitter in the forward direction, the receiver receives only the AM1 signal (represented by a solid line in the figure), and when the reception electric field is normal, the first reception signal is generated every time the reproduction clock ck2 rises. “1” is captured and held in all bits of the shift register 7, and “0” is captured and held in all bits of the second shift register 8 each time the reproduction clock ck 3 rises. In the first AND means 9, the input from the first shift register 7 and the inverted input from the second shift register 8 are all "1", so that the output is "1". On the other hand, in the second AND circuit 10, the inverted input from the first shift register 7 and the input to the second shift register 8 are all "0".

After the vehicle has passed through the transmitter in the forward direction, the receiver receives only the AM2 signal (represented by the dotted line in the figure). When the received electric field is normal, the first shift register is activated every time the reproduction clock ck2 rises. 7, "0" is captured and held in all bits, and "1" is captured and held in all bits of the second shift register 8 every time the reproduction clock ck3 rises. In the first AND means 9, the input from the first shift register 7 and the inverted input from the second shift register 8 are all "0", so that the output is "1". On the other hand, in the second AND circuit 10, the inverted input from the first shift register 7 and the input to the second shift register 8 are all "1".

Therefore, when the outputs of the first AND circuit 9 and the second AND circuit 10 are "1" and "0", A
The M1 signal is being received, and this output is "0" and "1".
In this case, the AM2 signal is being received. Thus, the first
By changing the outputs of the AND means 9 and the second AND circuit 10 from "1" and "0" to "0" and "1", it can be identified that the traveling direction is the forward direction. The same applies to the case where the traveling direction is reversed, but the description is omitted.

Next, in the case of an instantaneously weak reception electric field, for example, when the traveling direction is the forward direction and the transmitter has not passed, a part of the bits of the first shift register 7 is set to "0" by the input of the AM1 signal. In this case, the output of the first AND means 9 changes from “1” to “0”, while the second AND means 1
This is the same as described in the related art section in that the output of 0 holds “0”.

Next, in the case of a weak reception electric field for a certain period, for example, when the traveling direction is the forward direction and the transmitter has not passed, the input of the AM1 signal is affected as shown in FIG. All bits change from “1” to “0” and the second
All the bits of the shift register 8 hold “0”. Therefore, both the outputs of the first AND means 9 and the second AND means 10 become "0". As in the prior art, all the bits of the first shift register 7 or the second shift register 8 are stuck at "0" due to the failure of the receiver in which the shift register extracts the AM signal, and further the first AND means 9 Alternatively, when a state occurs in which the second AND circuit 202 is stuck at a high level, one of them is fixed to “1” and the other is fixed to “0”. Therefore, it has become possible to distinguish this failure from a state due to a weak reception electric field for a certain period.

FIG. 3 is a diagram showing a specific example of the traveling direction identification circuit of FIG. In the specific example shown in this figure, AM modulation is performed with a 1 KHz square wave, an 8.192 MHz oscillator is used as the clock generation means 3, and the synchronization means 4 and the 90 ° phase shifter 5 are used as the clock generation means 3. A timing generation counter (HC393) for generating the reproduction clock ck1 and the reproduction clock ck2 based on the clock signal is used. Also, data is taken in using the reproduced clock ck1 and the inverted reproduced clock ck3 as synchronization signals, and the shift register HC164 is used as the first shift register 4 and the second shift register 5.
In the above, the case where the AM signal in the case of the weak reception electric field is not completely present for a certain period has been described.
There may be an unstable state that has changed.
In this case, erroneous recognition may be caused in the traveling direction before passing immediately below the beacon, which is a wireless device. That is, the traveling direction is determined when the reception electric field is weak, and the traveling direction is determined again when the vehicle passes just below the beacon. If the weak reception electric field is frequently repeated, the identification of the traveling direction becomes unstable due to noise. The prevention of false recognition in this case will be described below.

FIG. 4 is a diagram showing another example of the moving direction discriminating circuit of the moving body according to the embodiment of the present invention. The traveling direction identification circuit 150 shown in this figure is almost the same as that in FIG. In this figure, the first AND circuit 9 and the second AND circuit 10 are respectively connected to two AND circuits 91, 92 and 93 and 1
01, 102 and 103 only. Next, the stabilizing circuit 151 provided in the traveling direction identification circuit 105 will be described. The stabilizing circuit 151 has, for example, a frequency of 250 k.
Hz clock oscillator circuit 110, first and second 255 counter circuits 111 and 112 which count clocks of the clock oscillator circuit 110 and are preset to a count 255, and exclusive logic for inputting a reception signal from a receiver. A counter reset 113 comprising a sum circuit for resetting the counts of the first and second 255 counter circuits 111 and 112, and an integrator 113-1 for integrating a received signal to form a reset signal for the counter reset 113
A first latch circuit 114 for latching output data of the first 255 counter circuit 111 based on a reception signal from the receiver, and a second latch circuit 115 for latching output data of the second 255 counter circuit 112 And the second
And an inverting circuit 116 for inverting a received signal from the receiver to latch the latch circuit 115, and comparing the count numbers p1 and p2 latched by the first and second latch circuits 114 and 115 with a fixed count value 245. First and second comparators 117 and 118 and first and second comparators 117
AND means 119 for inverting and inputting the output of the first and second 255 counter circuits 111 and 112 and inputting them to form an output signal E, the output of the AND means 119, AND means 120 and 121 for inputting the outputs of the first AND means 9 and the second AND means 10, respectively;
And a traveling direction detecting means 122 for detecting the traveling direction of the vehicle based on the output of the vehicle.

Next, the operation of the stabilizer 151 will be described. The oscillation frequency of the clock oscillation circuit 110 is 250 kHz
Therefore, a signal of 250 cycles is generated in 1 ms, and the first and second 255 counter circuits 111 and 112 change the reception signal of the receiver from “H (high)” to “L (low)”. , Or vice versa, and the counting is started. In the first latch circuit 114, when the input signal from the receiver changes from “H” to “L”, the output data of the first 255 count circuit 111 is latched. In this case, the second latch circuit 115 does not latch by the inverter 116. Conversely, when the input signal from the receiver changes from "L" to "H", the second latch circuit 115 activates the second 255
Output data of the count circuit 112 is latched. In this case, the second latch circuit 115 does not perform the latch. First
In the 255 counter circuits 111 and 112, the carry signal is "H", and in other cases, the carry signal is "L". Also, the first
The output signals of the latch circuits 117 and 118 are “H” at p1, p2 ≦ 245, and p1, p2> 2
It is "L" at 45.

FIG. 5 is a diagram showing a timing chart in the traveling direction identification circuit of FIG. As shown in the figure, in the AND means 119, the received signal is continuously "H",
When it can be determined to be “L”, that is, when the duty ratio of the AM reception signal from the receiver is monitored and the value is within 50 ± 4% in this embodiment, an “H” output is formed,
Otherwise, an "L" output is formed. Therefore, if the output of the logical product means 119 is "H", the output signals "1" and "0" of the first and second logical product means 9 and 10 or vice versa are directly passed through the logical product means 120 and 121. It is input to the traveling direction detecting means 122 to identify the traveling direction. On the other hand, if the output of the AND means 119 is "L", the signal of the AND output is obtained even if the output signals of the first and second AND means 9 and 10 are "1" and "0" or vice versa. 120
And 121 are both "0", and the traveling direction detecting means 122 stops identifying the traveling direction. Therefore, even if the noise and the AM signal are the same in frequency in the traveling direction identification circuit 150, they are distinguished by the duty ratio and the operation of the bidirectional identification circuit 150 is prohibited in the case of noise. The traveling direction of the vehicle, that is, the signal immediately below the beacon, which is a wireless device, can be stably identified.

[0029]

As described above, according to the present invention, not only when a weak reception electric field is generated instantaneously, but also when a square wave is not formed by the weak reception electric field for a certain period of time, the signal can pass immediately below the beacon. This is also distinguished from the phenomenon of the failure of the traveling direction identification circuit. In this case, the traveling direction is not determined, and erroneous identification of the traveling direction is prevented. In addition, due to the weak reception electric field, it is affected by noise and monitors the duty ratio of the square wave,
If the duty ratio deviates from a certain range, it is determined that the received electric field is weak and noise is mixed in, so that the identification of the traveling direction is not performed, and the instability of the identification can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a traveling direction identification circuit of a moving object according to an embodiment of the present invention.

FIG. 2 is a diagram showing a timing chart in the traveling direction identification circuit of FIG. 1;

FIG. 3 is a diagram showing a specific example of a traveling direction identification circuit shown in FIG.

FIG. 4 is a diagram illustrating another example of the traveling direction identification circuit of the moving object according to the embodiment of the present invention.

FIG. 5 is a timing chart in the traveling direction identification circuit of FIG. 4;

FIG. 6 is a diagram showing an outline of a roadside-vehicle communication system of a mobile body.

FIG. 7 is a diagram illustrating data provided from the wireless transmitter of FIG. 6;

FIG. 8 is a diagram showing a conventional circuit for identifying a traveling direction.

9 is a diagram showing a timing chart of the operation of the traveling direction identification circuit of FIG.

FIG. 10 is a diagram showing a decrease in the level of an AM reproduction signal when a reception electric field is weak.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Antenna 2 ... Receiver 3 ... Clock generation means 4 ... Synchronization means 5 ... 90 degree phase shifter 6 ... Inverter 7 ... 1st shift register 8 ... 2nd shift register 9 ... 1st logical product means 10 ... Second logical AND means 110... Clock oscillating circuit 111, 112... 255 counter circuit 113... Reset circuit 114, 115... Latch circuit 116, inverters 117, 118. Traveling direction detecting means 150: Traveling direction identification circuit 151: Stability circuit

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-133527 (JP, A) JP-A-1-92611 (JP, A) JP-A-5-290295 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G08G 1/09 G08G 1/0968 H04B 7/26

Claims (2)

(57) [Claims] 1. A traveling direction discriminating circuit for a mobile unit, which indicates road information data from a wireless transmitter installed on a road and a traveling direction synchronized with the road information data and receives square waves having mutually opposite phases. And a reproduction clock ck2 and a reproduction clock c having the same cycle as the square wave indicating the running direction and having a phase shift of 90 °.
clock generation means (3) for forming a reproduction clock ck3 having a phase opposite to k2; a first shift register (7) for taking in and shifting a square wave indicating the running direction as bit data for each reproduction clock ck2; A second shift register (8) that takes in and shifts a square wave indicating the running direction as bit data for each of the reproduction clocks ck3; and each bit data taken into the first shift register (7) and the second shift register. First AND means (9) which takes the logical product of the bit data taken in and inverted by the second shift register (8), and each bit data taken and inverted by the first shift register (7) And the second shift register (8)
And a second logical product means (10) for performing a logical product of the respective bit data taken in the moving object. 2. The method according to claim 1, further comprising: providing road information data from a wireless transmitter installed on the road, and providing a square wave having a phase opposite to that of the wireless transmitter in a direction opposite to the wireless transmitter in synchronization with the road information data. A traveling clock identification circuit for receiving a moving object, wherein the reproduction clock ck2 and the reproduction clock c have the same period as the square wave indicating the traveling direction and are shifted by 90 ° in phase.
a clock generation means (3) for forming a reproduction clock ck3 having a phase opposite to that of k2, a first shift register (7) for taking in and shifting a square wave indicating the running direction as bit data for each reproduction clock ck2; A second shift register (8) that takes in and shifts a square wave indicating the running direction as bit data for each of the reproduction clocks ck3; and each bit data taken into the first shift register (7) and the second shift register. First AND means (9) which takes the logical product of the bit data taken in and inverted by the second shift register (8), and each bit data taken and inverted by the first shift register (7) And the second shift register (8)
A second AND means (10) for calculating a logical product of the respective bit data taken into the memory, and a duty ratio of the square wave, and the first and second logical product means only when the duty ratio is constant. And a stabilizing circuit (151) for passing the outputs of (9) and (10).